1. Field of the Invention
This invention relates to a thermoplastic polymer alloy with asphalt that is useful in the road paving and roofing industries. More particularly, this invention relates to the reaction and resultant linking of epoxide-containing polymers to asphalt forming a polyepoxy-polymer-linked-asphalt composition having improved high temperature resistance, improved high elasticity at ambient and low temperatures as well as good toughness and tenacity values.
2. Description of Related Art
The use of polymers as additives to asphalt (bitumen) is well known in the art. See for example U.S. Pat. Nos. 4,650,820 and 4,451,598, both incorporated herein by reference, wherein terpolymers derived from ethylene, an alkyl acrylate and maleic anhydride are mixed with bitumen. Also, see for example U.S. Pat. Nos. 5,306,750 and 6,117,926, both incorporated by reference, wherein reactant epoxy-functionalized, particularly glycidyl-containing, ethylene terpolymers are mixed and reacted with bitumen and, preferably (as taught in U.S. Pat. No. 6,117,926) with a catalyst to accelerate the rate of reaction and lower cost of the modified system.
Today""s asphalt pavements require good resistance to high temperatures coupled with good low temperature properties as defined by SHRP values. In addition, elastomeric properties are desired by Departments of Transportation (DOT""s) to give resistance to low temperature cracking, to fatigue and to rutting. These elastomeric properties are defined by ductility at room and low temperature, elastic recovery, toughness and tenacity. Particularly useful polymer-modified asphalts generally meeting these requirements are the polyepoxy-polymer-linked-asphalts that are made by a process described in U.S. Pat. No. 5,306,750 patent to J. L. Goodrich and R. J. Statz. The reaction described in U.S. Pat. No. 5,306,750 can be enhanced as provided in U.S. Pat. No. 6,117,926 patent to Engber.
While it is possible to produce particularly useful polymer-modified asphalt using the processes described in U.S. Pat. Nos. 5,306,750 and 6,117,926, there is still a need for polymer-modified asphalt with improved high temperature resistance as well as improved elasticity at both ambient and low temperatures. There is also a need to provide polymer-modified asphalt that has good toughness and tenacity. Further, polymer-modified asphalt reaction products with relatively low viscosities (low enough to allow easy application) at application temperatures (about 140xc2x0 C.), high ring and ball softening points (greater than 75xc2x0 C., preferably greater than 100xc2x0 C.) and a high degree of elasticity (greater than 75% after 300% stretch) are desired.
It is also desirable to be able to meet comparable SHRP standards while employing glycidyl-moiety-containing-ethylene copolymers having lower glycidyl moiety content than typically employed to get the SHRP values, thus reducing the cost of the polyepoxy-polymer-linked-asphalts.